| Wheel loader is an engineer machinery with high efficiency in loading,which is used extensively and has already become a main force of industrial world。In the future time, the requirement of it in domestic market will keep on a high level continually which will cause the domestic loader production factories expand sharply, thus making the competition in this field even more fiercely。Factories develop new products of the kind in succession in order to meet the challenge of the market。The hydraulic system is an important part of the wheel loader, which is designed to own a high level of working capability。As the main part of the hydraulic system of loader,the temperature of hydraulic oil will be controlled at 35-85℃which is an ideal range。Because of this, the viscosity of liquid oil, lubrication wearability are in the best position and the system transmission is on the highest efficiency。The hydraulic system, when being used, would cause a sharp increase of the temperature of oil along with the exchanging of the thermal energy caused by the losing of pressure, volume and machinery。Secondly, the wear and tear of the hydraulic parts,the pollution of hydraulic oil, the air and the phenomenon of air corrosion would lead to the increase of the temperature of the system。,The reasons of causing the high temperature of oil in wheel loaderare so many, the soul elements are among the following:①the defect in design of hydraulic system②the unreasonable design and installationof pipeline③over-consume of volume④the machinery losing process causes a high temperature of liquid oil⑤over-high pressure leads to the higher temperature of liquid oil⑥the condition of heat transmission is invalidThat increase of temperature of oil would eventually lead to the change of its viscosity,thus cause a series of sabotages to the hydraulic system such as making the running unstable, lowering the quality of hydraulic oil,shortening the life span of hydraulic element,accelerating the process of oxidation of liquid oil, and finally bringing the overall sabotage to the seal,life span and efficiency of transmission of hydraulic system。keeping the oil temperature of hydraulic system in a certain range is the key point of the regular work of the loader。According to this,the analysis of heat transmission of the loader's hydraulic system has very important meaning。The loader hydraulic system's heat transmission may conclude the dissipation of the pipeline and the dissipation of the flat。On the other hand, the transmissive power of the hydraulic oil radiator decide directly whether the surplus heating would be transmited , and then influent the regular work of the hydraulic system。The purpose of this thesis is to give an systematic study of the cause of high temperature of liquid oil, and aim at finding a practical way to reduce the high temperature within the system。An Investigation of a 50 wheel loader is systematically carried out,in which ,the test of working assembly line of hydraulic system is given respectively, and every main element, the pressure and temperature is carefully measured under the various working conditions in its hydraulic systemas well as in its steer gear (changing direction)。According to the formly approach to the hydraulic system transmission , such as increasing the dissipated area of hydraulic oil radiator will not be the effective way to solve this problem。After the design of the loader, the radiator,the electric fan and the pump would be newly fixed。Because of this outer influence, vehicles heat transmission system's cool wind, cool water, machine oil, hydraulic oil and transmission oil will not agree with the assumed status。So that the system's heat transmission falls into the tendency which is far from the design value, thus gives rise to the heating of the system。The thesis also confirms and reveals some basis causes of over-high temperature of oil,such as①over-smaller volumn of the tank whichcauses the inefficiency of heat transmission②the low-power of radiator。Based on the above investigations, this paper presents the following possible solutions: raising the volume and area of oil tank, completely eliminate the air within the return circuit and select a reasonable pattern of arrangement of hydraulic oil radiator。...
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